西藏冈底斯带阿索构造混杂岩南侧亚布努马花岗斑岩地球化学特征及锆石U-Pb年龄  

Geochemistry and zircon U-Pb age of granite porphyry in the Yabunuma region close to the southern margin of the Asuo structural melange belt, Gangdise, Tibet

作　　者：李航 王明[1] 解超明[1] 曾孝文[1] 董宇超[1] 于云鹏[1] 罗安波 LI Hang;WANG Ming;XIE Chaoming;ZENG Xiaowen;DONG Yuchao;YU Yunpeng;LUO Anbo(College of Earth Science,Jilin University,Changchun 130061,Jilin,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061

出　　处：《地质通报》2018年第8期1510-1518,共9页Geological Bulletin of China

基　　金：中国地质调查局项目<班公湖-怒江成矿带铜多金属矿资源基地调查>(编号:DD20160026);<冈底斯-喜马拉雅铜矿资源基地调查>(编号:DD20160015);国家自然科学基金项目<青藏高原羌塘南部埃迪卡拉纪地层研究>(批准号:41602230);<班公湖-怒江洋早白垩世构造演化:来自复理石沉积的制约>(批准号:41702227)

摘　　要：西藏中冈底斯北部尼玛县阿索乡亚布努马地区东侧出露一处花岗斑岩岩脉,LA-ICP-MS锆石U-Pb测年结果显示,该花岗斑岩的形成时代为晚侏罗世(161.2±5.9Ma)。全岩地球化学数据显示其高硅、富碱、富铝的特征,属于碱性准铝质花岗斑岩;富集轻稀土元素,轻、重稀土元素分异明显,具有明显的负Eu异常,富集Rb、Pb等大离子亲石元素,亏损Ba、Sr元素及Nb、Ta、Ti、U等高场强元素,形成于岛弧环境。其源区可能为来自俯冲带增厚下地壳的深熔作用,结合区域上同时代的岩浆事件,亚布努马花岗斑岩应该形成于以班公湖-怒江洋南向俯冲为动力背景的陆缘弧环境。The granite porphyry vein in the Yabunuma area is located in Asuo and Nyima area of northern Central Gangdise.LAICP-MS zircon U-Pb age of 161.2±5.9Ma indicates emplacement during the Late Jurassic.The bulk rock geochemical analyses indicate the characteristics of high silica,rich alkali and Al,suggesting alkali metaluminous granite porphyry.The granite porphyry samples are rich in LREE,the fractionation between LREE and HREE is strong and shows obvious negative Eu anomalies,with the characteristics of enrichment of Rb and Pb,depletion of Ba,Sr,Nb,Ta,Ti and U,suggesting an island-arc setting.The granite porphyry is likely to root in anatexis of thickened lower crust.Considering coeval magma event in the vicinity,the authors hold that granite porphyry from Yabunuma region should have formed in an active epicontinental environment on the background of the southern subduction of Bangong Co-Nujiang Tethyan Ocean crust.

关 键 词：中冈底斯 花岗斑岩 南向俯冲 深熔作用 陆缘弧环境 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]